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September 21, 2011

Effects of Spaying and Neutering on Behavior

Over the years, I've heard a lot of people/organizations that have claimed that people should alter their pets for a whole host of reasons. Generally, among the reasons listed is that it will make your pet less aggressive (this information is also sometimes used to justify laws mandating the spay/neuter of certain breeds/types of dogs).

While certainly there are a lot of good reasons to spay/neuter your pet (ease of population control being an important one), are the statements about improved behavior one of those?

Fortunately, there has been some research done on this topic. This research is not terribly new (the study was performed in 2006) but it has been sitting in my inbox to discuss for awhile and I've just never made the time to discuss it.

In the effects of spay/neuter study, they interviewed more than 1500 dog owners (all breed club members with dogs of known heritage) with dogs over the age of 1 year old. They had a 50/50 male/female ratio and 40% of the dogs were either spayed or neutered. In the interviews, the asked the dog owners to fill out the C-BARQ scorecard on a variety of different behavioral problems including:

- Stranger directed aggression

- Owner-directed aggression

- Dog-directed fear/aggression

- Dog Rivarlry

- Stranger-directed fear

- Nonsocial fear

- Separation-related behavior

- Attachment/attention-seeking

- Trainability

- Chasing

- Excitability

- Touch snesitivity

- Energy

Dogs from 11 different breeds were included - ranging in size from Yorkies to Rottweilers to measure differences among breeds.

The #1 reason people said they altered their pets was because of birth control (42%). But interestingly, 31% said to prevent health problems and 18% noted to control/prevent behavior problems. So behavior modification is a major driver why people alter their pets.

The results of the research may surprise you.

Spayed females were more aggressive toward both strangers and owners than intact females.

Spayed females were more fearful and sensitive to touch than their intact counterparts.

Neutered males were much less likely to mark their territories.

Both males and females that were altered were more likely to beg for food and to engage in excessive licking of people or objects.

The incidence of dog-directed fear/aggression varied quite a bit by breed. Some breeds: Bassett Hounds, English Springer Spaniels, Dachsunds, Labrador Retrivers and Yorkshire Terriers showed more aggression after being altered, where Golden Retrievers, Poodles, Shetland Sheepdogs, Rottweilers, Siberian Huskies and West Highland Terriers were either just as likely, or less likely to have shown aggression toward other dogs when altered.

In a second study, the researchers used a convenience sample of more than 3500 dog owners (76% of which were spayed or neutered) and measured the same criteria.

In this study, dogs of both genders were more likely to show dog-directed aggression/fear or owner-directed aggression when altered.

Dogs of both genders were also more likely to have touch sensitivity and non-social fear when altered.

Altered dogs were also likely to be less energetic.

Interestingly, for one breed-specific group in this survey, Doberman Pinchers, altered females were much more likely to show stranger-directed aggression, but altered males were much less likely to show stranger-directed aggression.

It should be specifically noted, that in all cases, the vast majority of all dogs studied showed no forms of aggression at all, regardless of their intact status -- and that differences in the scores don't mean that either situation results in severe behavioral problems.

In conclusion, the researchers report that for most behaviors, spaying/neutering was associated with worse behavior, contrary to popular wisdom, although a few behaviors (energy level, urine marking) were reduced with spay/neuter.

The effects of spaying/neutering were often specific to certain breeds, and not always equivalent between sexes.

I'm posting this information for a lot of reasons. I think there is a lot of "conventional wisdom'" that exists in animal welfare circles that has shown to not actually be grownded in actual data and I agree with the researcher's conclusions that if pet owners have a more accurate expectation of possible impacts of spay/neuter surgery they will be better equipped to prevent negative behaviors.

I also think it's interesting to read this in a world where many people want to link intact status to aggression and a reason for major dog bites. This may be true in at least some cases in male dogs, but definitely not for female dogs.

I also like their conclusion that similar research should be done with other proceedures similar to spay/neuter (like tubal ligation and vasectomies) to see if those can create the desired results (ease of population control) without the possible negative impact of lost hormones.

Does this change the way we promote spaying/neutering as a form of population control? Should it? Does it change whether or not cities should try to make laws mandating spay/neuter for public safety (certainly, there is no support for this in this research, in addition to the reality that it doesn't work to control population)? Certainly population management is essential to rescue success....but are there better solutions?

Addendum: I should have also noted on this study (and it was wisely pointed out below) that the study is not neccesarily a causal study because all of the other factors were not isolated. So the study does just measure a correlation between spay/neuter and behavior types -- that is not necessarily causal. There is also the issue of whatever variable that comes with owners defining the behaviors vs scientifically defining the behaviors. That said, I do think the study is interesting at the very least...

Comments

I wonder how many people who read this thinks that they are learning cause/effect relationships about behaviors. For example, the altered dogs who were more sensitive to touch than their unaltered counterparts. I wonder if the unaltered animals were more likely to be shown than the altered ones and so the unaltered ones were given more training/socialization in allowing strangers to touch them. As you've pointed out many times before, there are just SO many factors that shape a dog's behavior that I hope that no one sees any of the results from this study as a reason not to alter any more than it is a reason to alter. Thanks for sharing this study. Interesting stuff.

I would be very cautious about pointing out correlation from a survey. This is not a rigorous scientific study that eliminates all variables. To date, there is not ample evidence that castration increases aggression.

I'll read the complete study, but there is still a lot of difficulty in garnering biomedical data from a behavioral survey.

Lori/Marji - -a very fair statement about whether this is all causal, or just correlation. I had intended to put in a note about this in the post (I will go back and add) because obviously this is a factor -- as well as the reality that it is reliant on owner-evaluation of the behavior and not scientific evaluation.

I went to a seminar awhile ago presented by Dr. Chris Zink, who is a big name in veterinary sports medicine. Now, she will be the first person to tell you that her talk is directed toward a specific group of dog owners, those who are active dog sport participants, but it was very important to her that we speak truthfully about the benefits and risks of spaying and neutering.

She also talked about this study, as well as one from 2009 done by the Viszla Club of America. She also said that 11 of 13 scholarly papers written on behavior in connection to spay/neuter have determined that spay/neuter is detrimental. I don't have any citations, unfortunately.

I feel very strongly that spay/neuter is not and should not be a cookie-cutter issue. Hormones are important for so many reasons, and it makes sense that taking those hormones away, especially in a developing pup, would alter more than just fertility.

I also altered six month old bitches (my first pit bull, and a rescue pit bull) and never observed any adverse affects in those two particular dogs. They both lived longer than any other dogs I've owned, coincidentally.

I had a rescue pit bull bitch that was already spayed at five months when I got her and she developed ACL problems, but there's no way to know if she would have had the same problems otherwise.

As far as I know purebred cat breeders send their kittens to new homes already spuetered and have not noticed adverse side effects in cats like we've seen in dogs, but the physiology is completely different.

i can't count the number of times i've come across somebody with a young, unaltered dog with behavioral problems who says 'oh, it's not a big deal: this behavior [food aggression, object guarding, marking, humping, dominance, fear of other dogs, etc.] will end as soon as we get max fixed.'

and of course, six months later, the dog is doing the same exact thing, despite being spayed/neutered. only it's a lot less cute, because max is now bigger and stronger and more set in his ways than ever (btw, the worst humper i have ever come across was a neutered scottish terrier mix).

the only 100% sure thing you accomplish by spaying and neutering your pets is making sure they don't accidentally reproduce. behavior is far more complicated, and rarely a quick, ahem, "fix."

Thank-you so much for considering an academic source and sharing their findings.

A recent study (2008) in Queensland ("Report on the validity and usefulness of early age desexing in dogs and cats") considered early age desexing and suggested this may not be best practice for dogs, particularly female dogs. The research you've considered here may is another reasons to reconsider desexing of female dogs, at least.

I think there is a very loud mantra that exists, saying that responsible owners desex their dogs - and there is a stigma for owning undesexed dogs. This is as almost as pressing as any logical reason for desexing pets.

I thought Woody has a great point and the more I think about what W and arrowhead said the more it worries me...

Remember when people were saying "there has been no fatality by an altered pit bull". I thought that was asking for trouble at the time because I thought that statement alone promoted that altering pit bulls would ensure their safeness thus promoting BSL MSN. Well then, that woman was killed by her two altered male pit bulls when she was trying to break up a fight. While I believe altering males will decrease agression between them, once they LEARN to hate each other then altering won't magically erase that.

So to w & arrowheads point - if the owners of those dogs believed that altering would magically solve the behavior problems could that false belief lead to that woman's death? I might be stretching it a bit on this incident but at this point saying that altering will make a safer dog is unproven at best and a flat out lie that is jeapordizing people's safety at worst.

I believe most dogs/cats should be altered and most would benefit from it - not to mention most people do NOT want to deal with heat cycles. There is no reason to make stuff up when there are still plenty of benefits.

Shoshannah -- the study doesn't make any note of differences based on the age of alterations. Age of the dog at the time of surgery does seem to have health implications, so it would stand to reason that it might impact behavior too...but the study does not cover that.

Thank you for this post. I have just neutered my 1 year old Doberman and I've noticed a significant improvement in her behavior and thus I want to ask you if you can recommend out of experience some special accessories for neutered dogs. Both things to keep him happy and items to help cure her scar sooner.

Then there is the other affect, no more puppies to end up in shelters.

When we bring in unaltered dogs, male or female, the reaction from the team we have, is obvious, they react to the scents and posture of the new comer.

We gradually introduce them, and then the newcomer, is altered and peace returns.

We have seen differences in all ages, some males, regrettably still mark inside, even after altering and we have seen some male or female who still exhibit no change, in attitude, but through behavioral modification, most can be worked out.

Spaying and neutering reduces the pet population, which should be at the top of the to-do list.

I spent a lot of time socializing our new timid shelter dog. We were making great progress. Against my better judgment, and because I was compelled to do so by her adoption contract, I spayed her. One month later, it is as if I had never spent any time carefully desensitizing and socializing this dog. I have spent a lot of time with this dog and absolutely believe that her reversion to being scared of everything has something to do with the spay surgery - it's the only thing in her life that has changed.